The research will apply techniques used to study language acquisition in children to chimpanzees learning American Sign Language. A 2 1/2-year-old male chimpanzee, Nim, is living in a home with signing caretakers, and is being taught daily in a specially designed "classroom" to facilitate teaching and observation. He has acquired 47 signs, and combines them into sequences as long as 10 signs. The proposed research will extend his training and investigate the formal nature of his language behavior and its implications for his psychological development. A basic objective is to determine whether the multi-sign sequences of a chimpanzee share formal properties with sentences created by children. By the time Nim is 5 we expect that his active vocabulary will be approximately 350 signs. Special attention will be given to his learning pattern during the discovery of what each sign means and how to make it. The semantic bases of different multi-sign sequences will be evaluated, in part, by videotape analyses of their contexts. We will compare statistical models adequate to describe Nim's signing behavior with that of deaf children of hearing and deaf parents. We will investigate the implications of his signing for cerebral asymmetries, the relationship between cognition and language and the role of emotion words in the expression of emotion. The research will have practical and theoretical implications. Regular procedures for the "natural" acquisition of sign by chimpanzees will allow the broad study of traditional perceptual and cognitive problems in a non-human primate: that is, it will stimulate a field of comparative cognition. Isolation of the similarities and differences of the acquisition of sign in humans and non-humans will clarify the nature of language behavior. Finaly, experience with teaching a chimpanzee sign language may influence research on therapy for the handicapped.